1. Field of the Invention
This invention relates to a method for the control or prevention of aflatoxin contamination of commodities using non-toxigenic strains of Aspergillus flavus (A. flavus).
2. Description of the Prior Art
Aflatoxins are toxic compounds produced by fungi, particularly A. flavus and Aspergillus parasiticus (A. parasiticus), and are potent carcinogens that frequently contaminate agricultural commodities, especially during drought conditions, and are a serious threat to humans and animals [Cast, Counc. Agric. Sci. Technol. Rep., Vol. 80, (1979), Ames, IA., 56 pp]. The United States and most other countries prohibit aflatoxin levels in foods and feeds above 0.02 .mu.g/g (20 parts per billion) Schuller, et al., Proceedings of the International Symposium on Mycotoxins, 1983, pp. 111-129, Naguib, et al. (eds.), National Research Centre, Cairo. A. flavus produces aflatoxins B.sub.1 and B.sub.2 and is the primary cause of aflatoxin contamination of corn, cottonseed, and tree nuts [Diener, et al., Annu. Rev. Phytopathol., Vol. 25, (1987), pp. 249-270].
There are several instances where a plant disease problem can be prevented by forms of the organism that incites the problem. Frost injury to plants results from ice formation caused by ice nucleation-active strains of Pseudomonas syringae and Erwinia herbicola; strains of these bacteria that are not ice nucleation active can be used to competitively exclude ice nucleation active strains and thereby prevent frost injury (Lindow, S. E., Appl. Environ. Microbiol., Vol. 53, pp. 2520-2527). Several viral diseases of plants are managed by infecting the plants with mild strains of the inciting viruses; through cross protection, plants infected with the mild strains are protected from infection by more severe strains [Yeh, et al., Plant Dis., Vol. 72, (1988), pp. 369-460]. Nonpathogenic strains of Fusarium oxysporum can prevent infection of celery by pathogenic strains through competitive exclusion [Schneider, R. W., phytopathology, Vol. 74, (1984), pp. 646-653].
Cottonseed becomes contaminated with aflatoxins mainly following infection of pink bollworm-damaged bolls by A. flavus [Ashworth, et al., Phytopathology, Vol. 56, (1971), pp. 1104-1105 and Le, et al., Plant Dis., Vol. 71, (1987), pp. 997-1001].
Currently tests are available that determine the presence and amount of aflatoxin; however, there are no methods on the market for the prevention of large scale crop loss due to accumulation of unacceptable levels of aflatoxin.
It is an object of the present invention to provide methods for prevention of the accumulation of aflatoxins in agricultural commodities.